Head-to-Head Homocoupling of Ynamides via a Dual Activation Mode of Triple Bonds by Half-Sandwich Metal Complexes

Reported herein is the half-sandwich Rh-mediated head-to-head homocoupling of terminal ynamides to furnish dienyl bisamido rhodacyclic complexes, where the Rh–vinyl bond was formed selectively at the α-carbon to the nitrogen atom. This transformation was extended to include piano-stool Ru and Ir complexes to display an analogous homocoupling reactivity. Based on density functional theory studies, the reaction was proposed to proceed via a dual activation mode of the ynamide triple bonds: (i) generation of a zwitterionic keteniminyl metal species to induce an intramolecular chloride transfer and (ii) syn-carbometallation of the second coordinated alkynes by the alkenyl metal intermediate. An oxidative transformation of the homocoupled metal complexes gave multifunctional dienyl bisamide compounds.本文报道了半夹心型铑（Rh）介导的端基炔酰胺头对头均偶联反应，以制备二烯基双酰胺铑环金属配合物，该反应中铑-乙烯键选择性地生成在与氮原子相邻的α-碳位点。该转化策略可拓展至钢琴凳型钌（Ru）与铱（Ir）配合物，二者均展现出类似的均偶联反应活性。基于密度泛函理论（density functional theory）计算研究，该反应被提出通过炔酰胺三键的双重活化模式进行：(i) 生成两性离子烯酮亚胺基金属物种以引发分子内氯转移；(ii) 烯基金属中间体对第二分子配位炔烃进行顺式碳金属化。对该均偶联得到的金属配合物进行氧化转化，可得到多官能化二烯基双酰胺类化合物。